SC2: states of matter & mixtures Flashcards
(64 cards)
1
Q
the kinetic particle theory
A
describes the arrangement, movement & energy of particles in a substance
2
Q
how do solid particles vibrate?
A
around a fixed point
3
Q
what energy do solids have?
A
low
4
Q
how close are the particles in a solid?
A
very close
5
Q
what pattern do solids have?
A
regular
6
Q
energy in liquids
A
liquids have greater energy than solids
7
Q
how do liquids move?
A
slide past each other
8
Q
how are liquids arranged?
A
randomly
9
Q
how close are liquid particles?
A
quite close
10
Q
how much energy do gases have?
A
highest
11
Q
how do gas particles move?
A
quickly and randomly
12
Q
how close are gas particles?
A
far apart
13
Q
what arrangement do gases have?
A
random
14
Q
can solids be compressed?
A
no, they are close together and have no space to move into
15
Q
can solids flow?
A
no as particles have nowhere to move
16
Q
do solids have a definite shape and volume?
A
yes
17
Q
do liquids have fixed volume and shape?
A
fixed vol not shape
18
Q
can liquids be compressed?
A
not easily as their particles are close
19
Q
can liquids take the shape of containers?
A
yes as they can flow
20
Q
can gases be compressed?
A
yes as particles are far away from each other and have lots of space to move into
21
Q
do gases have a definite shape or volume?
A
no
22
Q
can gases take the shape of a container?
A
yes, as particles move quickly in all directions
23
Q
changes of state
A
transformations of matter from one state to a different one (physical change only, no more substances made)
24
Q
melting
A
solid to liquid
25
evaporate
liquid to gas
26
freezing
liquid to solid
27
condense
gas to liquid
28
sublimation
a change directly from the solid to the gas without becoming liquid
29
melting, evaporation & boiling
-particles in the solid have enough energy to overcome the forces between them
-they break out of fixed arrangement and move more freely
30
condensing & freezing
-energy is transferred from a substance to the surroundings when a substance
-the particles lose energy and bonds form between particles
31
what is particle theory?
scientists understanding of solids, gases & liquids
32
what are some limitations of particle theory?
-it doesn’t consider the forces between molecules
-it assumes that all particles are spheres even though particles have complex shapes
33
predicting a physical state
-state of a substance at a given temp can be predicted if it's melting point & boiling point are known
-if given temp is less than melting point, then it’s a solid
-if given temp between melting & boiling points then it’s a liquid
-if given temp larger than boiling point then it’s a gas
34
pure substance
only one element or compound
35
mixture
two or more substances that are not chemically combined
36
element
only contains one type of atom
37
compound
2 or more elements chemically combined
38
what melting point does a pure substance have?
sharp
39
what melting point does a mixture have?
melts over a range of temperatures
40
when a pure substance changes state the temperature…
stays the same
41
when an impure substances changes state the temperature…
changes slightly
42
filtration
used to separate an insoluble solid from a liquid
43
why does filtration work?
the filter paper has tiny holes that are big enough to let small molecules and dissolved ions through
44
crystallisation
-used to produce solid crystals from a solution
-when the solution is warmed, some of the solvent evaporates and leaves a concentrated solution
45
solution
a mixture that forms when one substance dissolves another
46
solute
the substance that is dissolved
47
solvent
the substance in which the solute dissolves
48
how to obtain large, regularly shaped crystals in crystallisation?
-put the solution to into an evaporating basin
-warm it by placing the basin over a bunsen burner
-stop all the heating b4 the solvent evaporates
-pour excess liquid away & dry the crystals
49
simple distillation
-used to separate a solvent and solute in a solution
-the dissolved solute has a higher boiling point than the solvent, so when the solution is heated, solvent vapour evaporates from the solution, gas moves and cools & condense
50
simple distillation steps
1. the water is heated
2. water vapour is produced
3. water vapour cools, condenses & drops into the beaker
4. the water is condensed & the salt stays behind
51
fractional distillation
-used to separate different liquids from a mixture of liquids
-works because different liquids have different boiling points
-vapour rises through a column which is hot at the bottom and cold at the top, the vapour condenses when it reaches a part of the column that's below its boiling point
-liquid flows out of the column
52
paper chromatography
separates the mixtures of soluble substances
53
paper chromatography steps
1. water & ethanol solution is heated (the solvent)
2. as the paper is lowered into the solvent, some dye spreads up the paper
3. the paper has absorbed the solvents & dye had spread further up the page
54
stationary phase
the phase that does not move in chromatography (eg: paper)
55
the mobile phase
the solvent that moves through the paper & carries different substances with it
56
why do different substances move at different rates in chromatography?
-the different dissolved substances in a mixture are attracted to the two phases in different proportions
-this causes them to move at different rates through the paper
57
what does separation by chromatography produce?
-a chromotogram
-a paper chromatogram can be used to distinguish between pure and impure substances
58
how many dots would a pure and impure substance have?
pure = 1
impure = 2 or more
59
how can you tell if substances are the same in chromatography?
they have the same amount of spots, match in colour and travel the same distance up the paper
60
how to calculate the rf value
distance travelled by substance / distance travelled by solvent
61
paper chromatography steps
1. draw pencil line across paper 1-2cm from bottom
2. use pipette to add small spots of ink to the pencil line on paper
3. place the paper into a container with a suitable solvent in the bottom
4. allow the solvent to move through the paper and remove the chromatogram before it reaches the top
5. allow chromatogram to dry, then measure the distance travelled by each spot and distance
62
treating fresh water (steps)
-large objects removed by screening using grids
-coarse filter removes larger insoluble grit particles
-aluminium sulfate is added to clump smaller insoluble particles together, these settle in the bottom of a sedimentation tank
-a fine filter bed removes very small insoluble particles
-chlorine gas is added to kill harmful microorganisms
63
treating seawater
-seawater contains too much dissolved salt to be suitable for drinking
simple distillation used to treat it:
-seawater is boiled & the water vapour is lead away & cooled
-it condenses to form pure water, leaving the salt behind
64
facts about the distillation process
-expensive as large amounts of energy are needed to heat the seawater
-water produced by distillation is useful in the laboratory for dissolving substances (does not contain any dissolved ions that might interfere with a chemical analysis)
